Each human kidney has about a million nephrons.
The basic function of the nephron is to regulate water and soluble substances (especially ions) in the body by filtering it all out first, reabsorbing what should be kept and excreting the rest. This is a function vital to supporting human life.
The nephron filters the blood by several processes concentrating the filtrates, reabsorbing ions (such as sodium, potassium, calcium, hydrogen, bicarbonate, chloride, and ammonium ions), solutes (such as glucose, amino acids, phosphates, and so on) according to the body's needs under hormonal control, or from anti-diuretic hormones, aldosterone, parathyroid hormone, atrial-natriuretic peptide and others. In this process urine is produced, and in doing so, eliminates wastes from the body, regulates blood volume and blood pressure, regulates the levels of important electrolytes and metabolytes and regulates blood pH levels.